Photographic film is typically formed of a film base having photo sensitive emulsion layers coated thereon in which an image may be captured, typically in a camera. When cut into an elongated filmstrip, the film has a natural tendency to curl back on itself in both the elongated, axial direction and the width or transverse direction to a degree depending on the film base and the filmstrip dimensions. The filmstrip is typically packaged tightly wound in a cartridge and partially unwound within the camera for making exposures. The cartridge and filmstrip may be stored for a period of time and under varying conditions of temperature and humidity such that the filmstrip takes on an accentuated "core set" film curl. Film curl is evident in elongated negative filmstrips after processing prior to making prints and also in the shorter segments that negative filmstrips are cut into after photofinishing to fit the segments into an envelope with the customer ordered prints.
Automated photographic printers for making positive paper prints from image frames of processed negative filmstrips are well known in the photographic art. Most automated printers have a film transport mechanism for step-wise advancing the filmstrip an image frame at a time from a supply reel to a takeup reel or the like and through an image frame sized scanning gate and an exposure gate at a high speed. In the scanning gate, the density and color balance of the negative may be automatically read out, and exposure parameters may be calculated and stored in memory until the same image frame is advanced into the exposure gate. In both the momentary scanning and exposure operation, it is highly desirable that the image frame be held down fiat and then released for high speed advancement of the next frame.
Elongated negative filmstrips that are printed for the first time in filling a customer order are typically spliced together in the leading and trailing segments to form a continuous band wound on a supply reel and referred to herein as a "first order web". After exposure of the image frames the negative filmstrips are separated and sliced into segments that contain four or more image frames. After processing the prints made from a customer order, the negative filmstrip segments and the prints are re-united and packaged automatically.
At times, following inspection of the prints, it is necessary to reprint certain image frames of the shortened segments. In addition, at a later time, customers may order reprints of selected image frames for their own reasons. In order to efficiently make such reprints, it is necessary to attach the filmstrip segments in a spaced apart, end-to-end fashion, e.g. along one lateral edge of each filmstrip to a tow web as shown in FIG. 1, and referred to herein as a "second order web".
When the filmstrip segments 10.sub.1 -10.sub.n are so attached to the tow web 20, the leading ends 12.sub.1 -12.sub.n are separated from the trailing ends 14.sub.1 -14.sub.n of adjacent segments by gaps 16.sub.1 -16.sub.n of about 0.5 inches. Each filmstrip segment 10.sub.1 -10.sub.n includes a number, e.g. four, image frames 18.sub.1 -18.sub.4 Of standard 35 mm dimensions. The side attached tow web 20 may be coded with information related to each filmstrip, e.g. customer and order identification of the image frame to be printed and the number of prints that may be read out by the printer and used to control transport and exposure operations.
The tow web 20 effectively widens the transport path for the film segments through a printer and is engaged by drive rollers of a transport mechanism to advance the filmstrip segments 10.sub.1 -10.sub.n through the scanning gate and the exposure gate of the printer. For efficiency, the printer transport mechanism of a specific printer may be configured to transport only such spliced together segments 10.sub.1 -10.sub.n attached to the tow web 20. Since automated printers are more frequently used to make prints from original, elongated filmstrips transported during the first printing thereof, an accessory transport mechanism, which may be temporarily substituted for the primary transport mechanism, may be provided for the occasional printing of a run of spliced together segments.
The spliced together segments 10.sub.1 -10.sub.n exhibit a degree of core set film curl that varies from segment to segment resulting in upward (bowed centrally away from the aperture) and downward (bowed centrally toward the aperture) curvatures of the leading ends 12.sub.1 -12.sub.n which can cause "stubbing" of the ends in the transport process, particularly as the leading ends 12.sub.1 -12.sub.n enter the scanning and exposure gates. This inconsistent core set film curl may make it difficult for photofinishing equipment to handle the film during high speed printing transport. The film handling characteristics of transporting mechanisms vary widely and are typically preset or configured to accommodate an "average" film curl and are not readily adjusted without operator input. Thus, the equipment must be monitored, and halted if a malfunction occurs. Filmstrip segments that stub may be irreversibly damaged or have to be removed and be straightened, which may be difficult to do.
Various types of transport systems for advancing the filmstrip into and clamping arrangements for momentarily holding fiat the image frame in the scanning and exposure gates are disclosed in my commonly assigned U.S. Pat. Nos. 5,111,241 and 5,055,874 and in other patents and literature. In the '241 patent, a Bernoulli effect is employed to provide an air bearing to minimize contact and drag during advancement of the filmstrip across a linear array scanning gate. The apparatus of the '241 patent may be used with both first order and second order webs.
In the '874 patent, film flatteners contact and hold down the lateral sprocket hole edges of the filmstrip image frame in the exposure gate. The filmstrip in the '874 patent is deflected in a serpentine path before and after the aperture of the exposure gate by deflectors that also only contact the sprocket hole edges in order to overcome the tendency of the filmstrip to curl transversely. This approaches is designed for transporting a first order web. In U.S. Pat. No. 4,353,645, a film advancement and flattening apparatus for continuously connected or individual short filmstrip segments is disclosed. A rectangular flattening frame having longitudinal and transverse frame members is attached to a solenoid operated, side mounted, hinged rocker. On operation of the solenoid rocker, the frame is lifted on the side mounted, hinged rocker during filmstrip advancement and rocked downward to engage the sides of the image frame against the stationary frame surrounding the exposure aperture. The side mounting and rocking motion presents the lower side of the transverse edges of the movable transverse frame members in an interfering position with upwardly bowed or curled filmstrip segments, resulting in stubbing of the leading end thereof. To alleviate this problem, it is suggested that the interior edges of the movable transverse frame members be curved, rather than straight. It is represented that the curvature deflects the upward bowed leading edge of a film segment downward so that it does not catch.
In a further prior art system employed with automatic printers manufactured by the assignee, film flattening in the exposure gate was effected by movable "picture frame" members positioned above and below the filmstrip which were moved apart to a rest position during filmstrip advancement and clamped together to hold the image frame fiat. The movable frame members were upstream and downstream, upper and lower, transverse clamping members. Stubbing of the leading ends of filmstrip segments advanced by the web is avoided by widening the rest position of the transverse clamping members. Doing so increases the path of travel and the time taken, which slows the overall transport speed and hourly printing rate of the printer. Scratching of the filmstrip image frame could also occur during transport to the next image frame.
These approaches, to the extent that they work in alleviating stubbing, are inefficient in that the operating speed of the printer is slowed by the speed of movement over the path of travel of the moving components of the flattening apparatus.
In a further context, it is known to flatten and position image frames of filmstrips with respect to an aperture and frame in order to scan the frames to digitize and record the digitized information for reproduction in a video format. For example, photographic image frames are scanned and the image data derived from the scanning is transformed into a video bit stream employed in the recording of a compact video disc for "photo-CD" playback. Such filmstrip image frame flatteners are described in commonly assigned U.S. Pat. Nos. 4,965,632 and 5,028,956 and in the above cross-referenced applications. In the filmstrip flatteners disclosed in the '632 and '956 patents, image frames are stretched or tensioned laterally as a line contact gripping member is brought to bear along and upon one of the longitudinal image frame edges and pressed laterally to effect the lateral stretching while the other longitudinal edge is held stationary. The stretching is accomplished by slightly flattening tensioned arms connecting the line contact gripping members. It is difficult to maintain alignment of the line contact gripping members and to maintain constant stretching force and resulting lateral flatness because the tensioned spring arms fatigue and change shape over extended use.
Moreover, no control is exerted over the leading and trailing edges of excessively curled filmstrips by the film clamping apparatus disclosed in the '632 and '956 patents. In this regard, the leading and trailing edges of the first image frames of a curled filmstrip make it particularly difficult to flatten those frames with the apparatus disclosed in the '632 and '956 patents.
In the above referenced '635 and '894 applications, shaped, compliant material strips are employed as longitudinally and laterally extending clamping elements in a picture frame type mechanism for applying normal force to the image frame edges. In the approaches of the '635 and '894 applications, the shape and resilience of the material used for the clamping elements is relied on to provide some laterally extending force when the clamping element is deformed under high normal force. The normal and lateral force vector is achieved on buckling of the side walls of the shaped clamping elements.
These approaches are dependent on material selection to achieve lateral stretching of the filmstrip image frame, and it is difficult to achieve consistent and correct forces at the film/platen interface. Moreover, these approaches do not address the problem of providing high speed transport and handling of second order webs into the film clamping apparatus.